Be grateful if someone could remove my daily edit limit.
Thank you
I know this is an old topic, but the bat monitor made me realise that this should be snoopable with a basic telephone pickup coil and a PC soundcard (or even an old style cassette tape adaptor - the ones which used to be used to couple MP3 players into car players)
25khz is well within the capabilities of PC cards and the frequency response of such coils (or the capabilities of a RasPi)
There are a number of audio serial decoder programs floating around in the ham radio community (including a few arduino projects), so this shouldn’t be hard to interface if one wanted to take that route